1. Field of the Invention
The present invention relates to a precision rotator used in a magnetic read/write apparatus.
2. Description of the Background Art
FIG. 6 is an elevation with partial section showing a background-art rotating drum device with fixed axis of helical-scan system used in a magnetic read/write apparatus. In this figure shown are a head 1 for reading/writing a signal from/to tape, an upper drum 2 (rotating drum) rotating with the head 1 attached thereto, a lower drum 3 (fixed drum) having a lead groove for guiding the tape, an axis 4 working as a center of rotation of the upper drum 2 and press-fitted to the center of the lower drum 3, a ball bearing 5 with its outer ring press-fitted to the upper drum 3 and its inner ring fit to the axis 4 allowing the upper drum 2 to rotate, an end ring 6 for applying pre-load to the inner ring of the ball bearing 5 in a direction of the axis from above the upper drum 2, a motor drum 7 fixed to the end ring 6 for rotating the upper drum 2 and a rotary transfer unit 8 for transferring the signal from the rotating drum side to the fixed drum side.
FIG. 7 is an elevation with partial section showing a background-art rotating drum device with rotating axis of helical-scan system used in a magnetic read/write apparatus. In this figure shown are the head 1 for reading/writing a signal from/to tape, the upper drum 2 (rotating drum) rotating with the head 1 attached thereto, the lower drum 3 (fixed drum) having the lead groove for guiding the tape, the axis 4 working as a center of rotation of the upper drum 2, the ball bearing 5 with its outer ring press-fitted to the upper drum 3 and its inner ring fit to the axis 4 allowing the upper drum 2 and the axis 4 to rotate, the end ring 6 for applying pre-load to the inner ring of the ball bearing 5 in the direction of the axis, the motor drum 7 fixed to the end ring 6 for rotating the upper drum 2, the rotary transfer unit 8 for transferring the signal from the rotating drum side to the fixed drum side, a terminal transfer unit for transferring the signal between th head 1 and the rotary transfer unit 8 and a damper 10 for suppressing resonance during the rotation of the drum.
An operation of the device of FIG. 6 will be discussed. In the rotating drum device with fixed axis, the signal on the tape wound around the drum is read by the head 1 attached to the upper drum 2 which is rotated by the motor drum 7 and transferred via a lead (not shown) and the rotary transfer unit 8 and through the inside of the fixed lower drum 3 to a circuit. In this signal transfer, two ball bearings 5 are provided on the upper and lower sides of the upper drum 2, which are held between the lower drum 3 and the end ring 6 and to which pre-load is applied by the end ring 6, to stably rotate the upper drum 2.
Next, an operation of the device of FIG. 7 will be discussed. In the rotating drum device with rotating axis, the signal on the tape wound around the drum is read by the head 1 attached to the upper drum 2 which is rotated by the motor drum 7 and transferred via the terminal transfer unit 9 to the rotary transfer unit 8 and further through the inside of the fixed lower drum 3 to the circuit. In this signal transfer, two ball bearings 5 are provided on the upper and lower sides of the lower drum 3, which are held between a flange 15 press-fitted to the upper end portion of the axis 4 and the end ring 6 and to which pre-load is applied by the end ring 6 in the direction of the axis, to stably rotate the upper drum 2. Further, in the drum with rotating axis, since there occurs torsional resonance of the axis, the dumper 10 for attenuating resonance is provided below the motor drum 7.
Having the above constitutions, the background-art rotating head devices have necessity for providing two ball bearings 5 on upper and lower sides of the axis 4 and applying constant pre-load to the ball bearings 5 by the end ring 6 to fix and stably rotate the head 1 about the axis 4. Further, since the axis 4 is hold by the two ball bearings 5 and the center of rotation of the upper drum 2 depends on the positional accuracy of the ball bearings 5, there arises problems that the center of rotation can not be corrected and so on.